In its broadest sense, a computer network is a set of nodes and communication channels which interconnect the set of nodes. The nodes may be computers, terminals, workstations, or communication units of various kinds and may be distributed at different locations. They communicate over the communication channels which are provided by the owner of the computer network or leased from a common carrier. These communication channels may use a variety of transmission media such as optical fibers, coaxial cable or twisted copper pairs. A local area network (or "LAN") is a computer network at a single site and, in many cases, is confined to a single building. A wide area network (or "WAN") is a computer network that uses either a public or private switching system to interconnect computers located at plural sites which may be separated by hundreds or thousands of miles.
There are a number of advantages to constructing a computer network. They include resource and data sharing, and communication and data exchange. Resource sharing provides users with convenient access to special computing resources, regardless of their physical location. Data sharing provides users with access to common databases. Data exchanges enable users to exchange data files while communication exchanges enable users to exchange messages, for example, via electronic mail (or "E-mail"). While networks may be arranged in a variety of configurations, a commonly used network design has a bus (also known as a "linear") topology in which a single network cable is routed through those locations where a data terminal equipment (or "DTE") device is to be connected to the network. At each of these locations, a physical connection (or "tap") is made to the cable to allow the DTE at that location to access the network.
At selected nodes of such a network, file servers or other large scale computer systems may provide network services while, at others of the nodes, individual workstations, each typically comprised of a personal computer (or "PC"), desktop computer, or other type of physically compact computer system capable of both operating as a standalone computer and accessing the network services, reside. While the precise configuration of any particular network will vary, for most networks used in business, PCs located at individual workstations predominate.
The components of the PC (as well as all other computer systems such as minicomputers and mainframes) may be divided into two functional units--the computing system and the human interface to the computing system For a PC, the computing system is, quite simply, the chassis and those devices--the motherboard, hard drive and the like--which reside within the chassis. The human interface, on the other hand, are those devices that humans use to transfer information to and/or receive information from the computing system. The most commonly recognized devices which form part of the human interface with the computing system include the monitor, keyboard, mouse and printer. Of course, a variety of other devices, for example, a joystick, trackball, touchpad or others too numerous to specifically mention, may form part of the human interface. For most PCs installed at workstations, the computer monitor, keyboard and mouse rest on the desktop while the computer chassis which holds the computing system rests on the floor underneath the desktop.
While the above-described network configuration is quite common in many business establishments, recently, a number of issues, in particular, security concerns, have been raised in connection with such network designs. Business contacts, vendor information, contracts, reports, compilations, proprietary software, access codes, protocols, correspondence, account records, business plans are just some of the fundamental assets of a company which are oftentimes accessible from an employee's computer where it can be quickly copied onto a floppy disk and stolen.
Disk and CD drives may also be used to introduce illegal, inappropriate or dangerous software to a computer. Storing bootlegged software can expose a company to copyright infringement claims. Computer games often reduce employee productivity. If imported onto a computer system, computer pornography may create a hostile work environment which leads to a sexual discrimination lawsuit against the company. Computer viruses can cause the loss of critical information stored on a computer. Finally, the computing system itself may be damaged or otherwise misconfigured when left accessible to technically oriented employees who take it upon themselves to attempt to repair and/or modify the computer system.
Another concern often raised in connection with the present practice of placing the computer system at the desktop is that such workstation designs actually work against proper maintenance of the computing system. When placed underneath the desktop, computing systems are often forced to absorb physical shocks when accidentally kicked, knocked over or struck by falling objects, any of which could result in damage to the various electronic components, located within the chassis, which comprises the computing system. Oftentimes, a computing system is placed in a "convenient" location and not in a location designed to keep it cool. A computer system typically includes a cyclonic fan designed to direct a constant flow of cooling area at the heat-generating components of the computing system. However, if a barrier is placed a few inches in front of the fan intake, the efficiency of the fan is reduced dramatically. Similarly, placing the computer system against a wall or running cables in front of the fan adversely affects the ability of the fan to properly cool the computing system. Finally, even in relatively clean office environments, the fan tends to draw in dirt and other dust particles into the interior of the computer chassis where they are deposited on the heat-generating electronic components which comprise the computing system. As dust tends to insulate the components on which it is deposited, the ability of such components to dissipate heat becomes degraded when a layer of dust collects on the component.
Logistical support, too, becomes a vexing problem for computer-intensive organizations when computing systems are scattered throughout a facility. When machine failures occur, the repair person must go to the machine to diagnose and repair the machine. Oftentimes, this entails multiple visits to the machine's location, particularly when the first examination reveals that replacement parts or a replacement machine are needed. Similarly, software upgrades and other performance checks become quite time-consuming tasks when personnel must travel to each machine where the software resides locally.
Finally, many office buildings were designed before the advent of the age of the PC. As a single PC can consume over 300 watts of power, a heavily computerized workplace could potentially demand power in excess of the amount available. Similarly, the heat generated by the large number of computers installed in modern workplaces can easily overwhelm the air conditioning capacity of a building's HVAC system, thereby causing room temperatures to rise above those levels preferred by the occupants of the building. This problem is expected to worsen as more computer systems include advanced processor subsystems, for example, those which include a Pentium II microprocessor manufactured by Intel Corporation of Santa Clara, Calif., which tend to generate greater amounts of heat than earlier, less powerful, processor subsystems.
By securing plural computing systems in one room, it is contemplated that many of the aforementioned security and maintenance concerns would be relieved. However, since most PCs are located at individual work stations and/or offices widely scattered throughout a place of business, to place the computing systems for multiple PCs in a common location, for example, inside a selected room, would result in the human interfaces being located at considerable distances from the computing systems coupled thereto. Traditionally, when coupling the computing system to the human interface, separate cables have been used for the analog video information stream generated by the computing system for propagation to the video monitor and the bi-directional digital data signals which are exchanged between the computing system and the remaining I/O devices such as the keyboard, mouse and printer which form part of the human interface. For example, a system may use three pairs of cables for the analog video information stream, one pair for the video synchronization information and one pair for the bi-directional digital data signals for each I/O device located at the human interface.
While simply lengthening the cables which couple the human interface to the computing system may appear to be a solution to the problem of multiple remotely located human interfaces which results when the associated computing systems are housed together, for example, in a common room, such a solution is not feasible because, as the distance between the human interface and the computing system is increased, the requisite size of the connecting cables also increases. As a result, the number and size of the cables needed to couple the various human interfaces to the associated computing systems would not only be unwieldy, it would be prohibitively expensive to install, particularly if one wanted to place large numbers of computing systems in the controlled access room and disburse the associated human interfaces throughout a building or office complex.
These concerns have also been driving the development of the network computer (or "NC") and other so-called "thin" computer solutions. While various NC designs have been proposed, most entail removal of the auxiliary memory (also known as the hard drive) and substantially reducing the size of the processor. All software applications and data files would be stored on the network and the NC would be limited to accesses of network software and data files. Most NC designs also propose that all disk drives (typically, the CD and floppy drives) be removed, thereby eliminating the ability of the NC user to import or export software applications and/or data files.
While the development of the NC is, at least in part, due to a recognition by the computer industry of security and other problems which have arisen during the evolution of computer networks, the NC is not a fully satisfactory solution to these problems. While removing some of the processing capability from the workstation, most NC designs propose leaving sufficient intelligence at the workstation to access the internet, load software applications retrieved from the network memory and perform other operations. In fact, many NCs hope to avoid the aforementioned cabling problems which arise for remotely located workstations by leaving sufficient intelligence at the NC to generate the stream of video information used by the video monitor to generate a display. Thus, while reduced in complexity, NCs will still have the maintenance, power and cooling concerns of existing PCs and other computer systems. Thus, while the NC represents a step in the right direction, many of the aforementioned issues cannot be resolved by wide-scale implementation of NCs.
In order to fully resolve the aforementioned issues, the entire computing system needs to be physically separated from the human interface. In our co-pending application Ser. No. 09/071,604 (Atty. Docket No. 10393.44) and previously incorporated by reference, we proposed keeping the human interface (monitor, keyboard, mouse and printer) at the workstation while relocating the associated computing system (chassis holding the motherboard, power supply, memory, disk drives, etc.) to a secured computer room where plural computing systems are maintained, for example, in a common support structure such as a rack. By securing the computing systems in one room, the employer's control over the computer systems would be greatly enhanced. For example, since employees would no longer have personal access, through the floppy or CD drive, to the memory subsystem, employees could not surreptitiously remove information from their computing system. Nor could the employee independently load software or other data files onto their computing system. Similarly, the employee could no longer physically change settings or otherwise modify the hardware portion of the computer. Maintenance would be greatly facilitated by placement of all of the computing systems in a common room. For example, the repair technicians and their equipment could be stationed in the same room with all of the computing systems. Thus, a technician could replace failed components or even swap out the entire unit without making repeated trips to the location of the malfunctioning machine. Such a room could be provided with special HVAC and power systems to ensure that the room is kept clean, cool and fully powered.
Recognizing that a network in which multiple computing systems, each coupled to a remotely located human interface still has considerable maintenance demands, we now propose to further simplify the network by coupling all of the remotely located human interfaces to a common computing system which presents itself as a virtual computing system to each of the human interfaces coupled thereto. It is, therefore, the object of this invention to provide such a computer network.